


A Study in Momentum

by KrisseyCrystal (AisukuriMuStudio)



Category: Doctor Who (2005), Sherlock (TV)
Genre: Angst, Angst and Hurt/Comfort, Angsty Schmoop, Death, Gen, Headcanon, Hurt/Comfort, Physics, Slight Johnlock - Freeform
Language: English
Status: Completed
Published: 2013-06-14
Updated: 2013-06-14
Packaged: 2017-12-14 22:25:48
Rating: General Audiences
Warnings: Creator Chose Not To Use Archive Warnings, Major Character Death
Chapters: 1
Words: 2,149
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/842061
Author URL: https://archiveofourown.org/users/AisukuriMuStudio/pseuds/KrisseyCrystal
Summary: <blockquote class="userstuff">
              <p>"It was like playing Icarus, really. They had always been a force themselves, chasing and chasing and fighting and marching forward, even when all odds were against them. So it seemed not only logical, but also inevitable that something would happen to them eventually.</p>
<p>Sherlock just didn’t think it would happen so jarringly soon."</p>
<p>Good thing, then, that there's a Doctor ready to come and pick up the pieces. </p>
<p>Heavy angst. Headcanon.</p>
            </blockquote>





	A Study in Momentum

_A heavy truck_ _moving fast has a large momentum._

_It takes a large and prolonged force to get the truck up to this speed._

_It also takes a large and prolonged force to bring it to a stop afterwards._

* * *

It was like playing Icarus, really. They had always been a force themselves, chasing and chasing and fighting and marching forward, even when all odds were against them. So it seemed not only logical, but also inevitable that something would happen to them eventually.

Sherlock just didn't think it would happen so jarringly soon.

And so jarringly flippantly.

* * *

_It's so wrong._

_Everything's so wrong._

* * *

Sherlock can't control himself. He hardly remembers anything, other than the  _red,_ and the blurs, and the motion and the shock-stutter-screech-halt of reality the same instant that bullet had been fired. He thinks he should remember more—he thinks there should be more recalling, more data saved of those last breaths that—that his blogger—John— _John—everything—("…Sher…Sherlock…" Wheeze. Cough. Flicker of vision. Everything blurs and fuzzes and he can't focus. Can't see that face that is home. "…p-please…"_ )

But when the raggedy man appears, and takes his arms and pulls him in a blue box, and he fumes and he writhes, and he  _is not himself—_ he cries— "—my momentum—I've  _lost—_ " –his voice cracks, unexpectedly so— _why? Why does it crack—_  "—I've lost my momentum."

The raggedy man has something so scarily  _familiar_ in his eyes as he mutters back, "I know, mate. Trust me. I know."

It is those words that ring around in Sherlock's head and finally make his vision clear, undistorted and unwarped by heavy shock, even as he still stumbles around this new space in a lost, dazed tizzy with his dirty, bloody clothes sticking to his skin. Momentum…momentum, he can't help but think—where did it go? He had been going so fast—so beautifully efficiently—inertia should have—but then— _p = mv_ —mass times velocity—Euler's first law—Newton's second law— _the rate of change of the momentum of a particle is equal to the force acting on it—_

—where did it all go?

* * *

_In his quiet moments, he reminds himself of a derailed train._

_Aimless._

_Alone._

_The engine's still there, still capable of working. It's got its coals, its wheels, its cars, compartments, funnel and everything—it can still run and work as good as any other automobile—_

— _but oh, what good is a train if it has lost its_ tracks _?_

_If there is nothing to ground it anymore and keep it focused, to hum and sing along beneath it when their metal harmonize together in perfect unity, uttering, "Fantastic!" "That's brilliant!" and urge him further and further into radiance by guiding him down the correct path he is supposed to go._

_What use is a train without her partner?_

* * *

"What use is a brain without a heart?"

The Doctor—ironic, really, that he insists on being called that, although Sherlock can't bring himself to refer to him as such—turns away from his contraption and for a second, looks completely surprised. Then he grins that awkward grin—that smile that says,  _Well, I'm honestly not quite sure how to respond, but here goes nothing, anyway—_ as he utters, "I wouldn't know. I've never met a living organism without both."

Sherlock scrunches his nose and turns away. "What about those…'Daleks' I've heard you speak of?" The word is strange and foreign on his tongue, and he doesn't like it. Doesn't like anything right now, really. "They sound as if they are…without a heart."

The Doctor hums, nodding, the smile slipping from his face as he considers that. He rolls back and forth on his heels once, bobbing up and down blithely as if his entire form is made of jelly, as he responds, "Ah—yes. Good catch, that, there—but actually, unknown by many, Daleks _do_ have a heart. People forget about it, or don't want to hear it, and indeed, it isn't the pride of any living organism to know, but your heart doesn't only love things. You need it to hate things, as well."

Sherlock doesn't make a sound or a nod in response.

* * *

_He often asks the Doctor why he took him away—why, out of all the billions and billions of human beings' timelines and lives did he chose to act at_ that  _moment, right in the middle of everything, to go and pull him out—and why he had ever thought such a thing, in the first place, would be a good idea and could help him somehow._

_It's in those moments that the Doctor looks the saddest, and Sherlock can't meet his eyes, because he suddenly_ knows  _that the Doctor knows what would have happened should Sherlock have been left alone._

" _Bit not good…?" Sherlock can't help but ask._

_The Doctor just gives him a flicker of a painful smile. "Bit not good, yeah."_

* * *

It's later, when Sherlock has finally come to terms with this new form of reality—that aliens exist—that there's such a thing as time travel—and that no, this said time travel  _cannot_ change what has happened those few weeks ago—that he finally turns to the Doctor and makes his sad request.

Part of him thinks that the Doctor will refuse and will turn him down, but then the raggedy man doesn't. Instead he just smiles warmly, sadly—somehow all the more understanding of Sherlock's broken state, and then with that sad, familiar look in his blue eyes and his bowtie all askew— as if he has been waiting for those words all along—he turns around and gives his contraption a  _whizz,_ a  _whirr,_ and a  _click_ , and the giant box groans as it moves back in time.

* * *

_A heavy truck_ _moving fast has a large momentum._

[ Sherlock. That has always been Sherlock. ]

_It takes a large and prolonged force to get the truck up to this speed._

[ And John, well…that had always been John. ]

* * *

This time, he sees everything.

And he  _wants_ to, because to not to would be a disservice to the man who has performed the greatest service of all. Both to Queen and Country, and to his Friend and Flatmate.

So he sees them—both of them—himself and John—wonderful, wonderful John— _SherlockandJohn; they had always been such an amalgamation, a contraction into one unified being—so of course the only thing that could ever separate them would be death—_ as they round the corner, running and running—and then he hears it.

The fire that changed everything.

_It also takes a large and prolonged force to bring it to a stop afterwards._

He watches with eyes that don't miss a detail as John's body stutters to a halt, feet tripping over each other as his jumper and jacket is suddenly stained dark, seeping, spreading red—and he hears the gasp, the absolute look of shock on his face—and watches as John falls, and as his own person suddenly comes to a stop as well.

He doesn't miss a thing as he watches his doppelganger shout hoarsely in surprise, "John…?" and watches the realization cross his own face as he remembered that he had legs that weren't made of iron but flexible tendons and running blood pumping through veins that could allow him to  _move—_ before he was suddenly there at his flatmate's side, pulling him onto his back as the red drips and drips and spreads, a growing ocean into which he remembered he had been drowning nauseously into—

—and it is then Sherlock crouches at the roof's edge, watching and listening and straining to hear every jagged breath his doctor had been struggling and failing to take, noticing the gradual pallor of his friend's lined face—how he looks so much older than before—as if he has more aged in five seconds than he would in a hundred years—and he notices how  _shocked_ John looked, or  _is_ looking. How…disappointed.

But not scared.

It is then Sherlock watches as those darkening blue eyes struggle up to meet Sherlock's. It is then he watches as those lips haltingly twitch to form desperate words even as his body begins to lax. Because this man, this incredible doctor himself, had  _known_ he didn't even have a second longer.

But still he wanted  _so much more._

"…Sher…Sherlock…"

Wheeze.

Cough.

Somehow still, lined with pain and worry and sorrow for everything he wouldn't be able to do, that face is home.

"…p-please…oh,  _plea_ … _se_ …God, let…m-me—"

The worst thing about it all is that he doesn't even get to finish.

Death comes far too quickly for some.

* * *

_It is a long time before Sherlock speaks again after that day._

* * *

The Doctor says he has only one more place to take Sherlock before dropping him back in his own time so no one—even Mycroft—will know he has been missing and safely grieving the loss of his only friend. Sherlock humphs, lets the crazy raggedy man take him wherever he wants to, because right now, he honestly doesn't care.

He just can't stop thinking about  _John_ and everything that had been so abruptly left unsaid, and everything that was now left undone and never completed. Never to be even known.

And everything that would  _forever_ be left...unknown.

Lost in his thoughts and musings—his mind palace now a darkened gothic building of shadowed, spider-web clustered corridors—he doesn't expect, and indeed hardly remembers the Doctor leaving him for a second once they had arrived at their destination, before he then comes back inside the TARDIS with something in his hands that is awfully familiar.

Sherlock narrows his eyes at it. "…why do you have my skull, Doctor…?"

But the man only grins. "Funny thing, this, really. You see, there was this older beekeeper who I met one day and who had told me some very interesting—and largely  _incredible_ stories. Very strange old man, but nice, somehow—as if someone else had told him to be and he hadn't stopped since. He told me, though, to come back and get this skull from him and to give it to a younger you once he died, because you would need it more than him. Something about…'conserving momentum,' or some other silly science thing that you two are both so very fond of. I haven't the faintest what he really means…but I think you would."

And indeed, Sherlock's face does slowly slacken in dawning comprehension.

The Doctor's grin only widens sympathetically and rather happily.

He pretends not to notice, then, how gently the consulting detective cradles the skull, fingertips brushing against eyeholes and nose-gaps as if the entire bone structure was a piece of china instead of a very good friend.

* * *

_In the law of the conservation of momentum, the amount of momentum exchanged between a pair of particles will always equal zero—so there is no actual change in the amount of momentum at any point in time, in any form of transference._

* * *

He knows now why the Doctor's eyes are so familiar.

Because he had seen them before—when the Doctor had given him his skull right after he recovered from his addiction. Those eyes had had that same knowing, sad look in them—as if weighing the entire world in a single glance and knowing both its darkest corners and lowest pits and yet still having the two hearts large enough to love them—when he had saved him from himself after John's death and when he gave him the skull of the man who would become his best friend.

The conservation of momentum.

John—it had always been John.

It was amazing to think that it had been John who he talked to late in the hours of night and early in the birth of mornings without even knowing it. John who he stared at when he had a particularly hard puzzle to work through. John who accompanied him on his first mystery and who accompanied him on his last.

Even before he had met the man, John had been there.

Incredible.

And so, it is John-on-the-mantelpiece who he now turns to, once the Doctor and he had said their farewells and he was left alone at Baker Street before Mrs. Hudson came home from Tesco—in order to ask a very poignant question that had been bugging him ever since the Doctor told him his story.

Hands folded behind his back, he murmurs very quietly so no one else can hear, "…how do you feel about bees, John?"

And even though there is no response, Sherlock lets a small smile curve his mouth anyway.

"Hm. Yes. My thoughts exactly."

* * *

_This conservation law applies to all interactions, including collisions and separations caused by explosive forces._

**Author's Note:**

> Sorry sorry. ;A; Although not sorry, really. Lots of angst, I know.
> 
> This entire thing was spurned from a oneshot-giveaway-spree I had for getting 50 followers on my Tumblr page. 8D Someone had very nicely requested that the Eleventh Doctor and Sherlock meet, so...I guess that's what made me start thinking of scenarios in which they would meet.
> 
> And then, of course...I got angsty for some reason today, out of the blue. So I came up with this.
> 
> The headcanon of Yorick being John's skull, given to Sherlock by the Doctor, came from another post on Tumblr that someone had made for the wholock-verse. It was too beautiful not to consider being headcanon. ;.; So I had to use it. All credit goes to them for their idea. It's absolutely wonderful.
> 
> Either way, I hope you've enjoyed, and I hope I haven't...hurt anyone too bad. ;A; I love you all! Thanks for reading! And have a wonderful day!


End file.
